Filter plugs for cigarettes



March 5, 1963v P. A. MUELLER FILTER PLUGS Foa CIGARETTES 3 Sheets-Sheet 1 Filed Nov. 12, 1958 INVENTOR. bvl flueg- March 5, 1963 P. A. MUELLER FILTER PLUGS FoR CIGARETTES 3 snets-sneetz Filed NOV. 12, 1958 INVENTOR.r 92u hay ma flflu? X A X x x X x X X 9 PJ H March 5, 1963 P. A. Mux-:LLER 3,079,929

FILTER PLUGS FOR CIGARETTES Filed Nov. 12, 195s s sneetssneeis Unite The present invention relates to lter plugs for cigarettes and to a method of manufacturing a lter -rope from brous material suitable for processing into such lter plugs, and to a device for the performance of the said method. The method can preferably be employed for the manufacture of a lter rope formed of a mixture of viscose bers and cotton and cellulose bers respectively.

A lter rope capable of being processed into lter plugs for cigarettes can generally be produced in one of two basically different processes depending on the different raw material employed.

If a paper-type raw brous material is used for raw material, no diiculties are generally encountered in the processing of such material. However, the ltering action of such materials is relatively small unless they are `subjected to a particular pretreatment. The pretreatment for such paper-type materials advantageously consists in a loosening of the ber structure of the paper employed, i.e. in disintegrating the material. With such pretreatment (see, by way of example the U.S. patent specications Nos. 2,228,383 and 2,707,960), anexcellent ltering action can be obtained so that such processes have already been largely adopted in practice.

However, if the raw material employed consists of bers and ber bundles, the principal diiculty resides in the necessity of taking measures designed to reinforce the lter rope formed of a bundle of bers. In the large majority of cases, a suitable binder must be employed to consolidate the ber tufts and to protect them against sliding displacement, which involves considerable disadvantages, such -as the emission in traces of solvents detrimental to health during smoking, or the inuencing of the taste. If such binders are not to be employed, the brous material must possess a sufficiently compact structure, such as that of cotton wool or the like, from which only lter plugs having an undesirable degree of resistance to pulling can be produced.

The present invention constitutes -a novel solution of the problems cited and it eliminates the former defects. lt relates to a lter plug for cigarettes comprising bers `and ber bundles and is characterized by the fact that a supporting framework formed of points of adhesion free from binders and solvents is provided between contacting bers Within the ber bundle, the mechanical strength of the bers located at the points of adhesion being increased at the expense of a lower adsorptiveand swelling power.

The invention further relates to a method of manufacturing such lter plugs characterized by the fact that at least one wide, loose web is produced rst from bers which comprise at least a portion of such synthetic bers which will form a point of adhesion when compressed, the said web being continuously passed between embossing means and thus consolidated by a pattern of points of adhesion between contacting bers. The self-supporting web is then gathered transversely lto the direction of travel and formed into a lter having a cross-section which is at least approximately circular.

The device according to the present invention for the performance of the said method is characterized by the presence of two mechanisms of which the rst one is provided, at the beginning of a conveyor line, with a pile web fabricating unit, possesses embossing means supplied by the conveyor line and equipped with take-up devices at the end of the conveyor, while the second mechanism States Patent A 3,-79,929 Patented Mar. 5, 1953 possesses -a gathering unit arranged at the end of a conveyor line designed to change a at pile web into a rope with a cross-section at least substantially circular, and which is designed to process the pile web delivered by the rst mechanism.

A number of embodiments of the invention is described in greater detail in conjunction with the drawing in which:

FIG. 1 is a perspective diagrammatic view of the lter plug according to the present invention;

FIGS. 2 and 3 are sketched representations of microphotographs of ber cross-sections;

FIG. 4 is a diagrammatic view of an embodiment of a device designed to consolidate a at material web;

FIGS. 5 to 9 are plan views of at ber webs provided with an embossed design;

FIGS. l0 and l1 are perspective views of a two-ply and three-ply ber web respectively;

FIGS. 12a, 12b are diagrammatic representations of an elevation and plan view respectively of a mechanism for producing a lter rope from a consolidated ber web; and

FIGS. 13a, 13b and 13C are diagrammatic cross-sections of ber webs.

The present lter plug 10 according to FIG. 1 as usual consists of a wrap 11 formed, by way of example, of thin paper enclosing a ber bundle 12 having an oval or circular cross-section. As shown by the front end of the lter plug, the bers 13 should substantially extend in the raxial direction of the plug. The entire ber bundle 12. is interspersed with a plurality of points of adhesion 14, which FIG. l shows only diagrammatically, between crossingor laterally contacting bers. These points of adhesion 14 can readily be found when such a lter plug 10 is opened either before or after using, and it canbe seen, c g. by means of -a magnifying glass, that the points of adhesion are produced not by bonding the contacting bers by means of a binder or solvent butby a mechanical deformation of the bers. Closer examination of the points of adhesion reveals that their mechanical strength is greater than that of the original ber but that the absorptive and swelling capacity of the said points of adhesion is substantially lower than that of the ber portions immediately adjacent such points of adhesion. Naturally, the points of adhesion are not necessarily points but may be elongated.

The ber bundle 12 reinforced by a plurality of points of adhesion 14 distributed at random is thereby provided, as it were, with a supporting framework of mechanically stable points of adhesion which will hardly be altered when used, and with unprocessed brous areas in the spaces between the said framework. The ber material in the spaces between the elements of these points of adhesion can substantially swell and become soft during use without markedly lessening the strength and stability of the ber bundle held together by the framework of points of adhesion. Against the lter plugs so far known, the strength of the lter plug is largely independent of the changes in strength of the bers during use. For this reason it is now also possible to employ highly absorbent ber material and to obtain -a high degree of ltering action despite low resistance to pulling.

The framework of points of adhesion within the ber bundle further has the advantage that the -smoke is positively conducted towards the highly adsorbent and/or absorbent ber material in the spaces. In particular this highly desirable effect can be enhanced or reduced by influencing the spatial arrangement of the points of adhesion within the ber bundle in the event of the lter plugs being produced in 'accordance with the method described hereunder.

For the manufacture of the lter plug according to this invention, a synthetic ber or lament formed of viscose,

ie., a regenerated cellulosic material, is employed by way of example, which is produced from cellulose xanthate in diluted caustic soda and forced through spinnerets in the form of viscous laments into a warm Spinning bath containing strongly saline diluted sulphuric acid. The bath causes the spinning solution to be precipitatedto form viscosel filaments which can be cut into desired staple lengths after washing and drying. l y

Such viscose bers or laments possess, by way of eX- ample, a specic gravity of 1.5 gms/cm? and a. specic strength of 22 to 41 kg./mm.2. VOn the other hand, cellulose acetate laments commonly have a specic gravity of about 1.3 gms/cm.3 and a specificstrength of 13 to 21 Vlig/mm?.

The' moisture absorption of 4such viscose bers or laments at 65% relative humidity amounts to about 13.5% and at 100% relative humidity to between 44 and 48% against the corresponding values of about 6.0% and 15% respectively in cellulose acetate bers. The synthetic viscose bers and filaments therefore display a far better absorptive capacity for moisture than cellulose acetate fibers. The reason therefor is found in the fact that the cellulose acetate bers largely adsorb moisture at the surface only while viscose bers absorb the liquid deposited on the surface in the interior of the ber thereby leaving the surface free to take up more moisture.

Absorption of moisture by viscose bers or filaments can easily be checked by their swelling and the enlargement of their cross-section. By way of example, FIGS. 2 and 3 show two types of viscose filaments in cross-sections enlarged at the rate of 1:550, the left side showing a lament in the dry state vas filament 13a and the right side showing the same filament in the swollen state as filament 13b. The enlargement ofV the cross-section, i.c. the enlargement of the surface within the outer fiber skin, is clearly Visible.

Examination of lter plugsformed of such hydrophile and swelling synthetic bers or filaments, preferably of various viscose fibershas shown that in order to obtain a satisfactory absorption of the liquid tar and nicotine components the synthetic bers or filaments should display an enlargement of the cross-Section of Yat least 100 percent after swelling. Moisture absorption should amount to at least yand 25% respectively in an atmosphere having a relative humidity of 65 and 100% respectively.

If these rules are observed, the lter plugs formed of such synthetic or regenerated cellulosic Ybers or laments will, if the above steps are taken to strengthen the lter bundle, Ydisplay an absoiptive effect considerably increased beyond that of cellulose acetate fibers. In addition, the hydrophilic and swelling synthetic fibers have behaviou-r of hydrophile synthetic bers has so far caused them to be considered entirely unsuitable for the purpose of ltering smoke.

However, practically all these defects can be removed if the bundle of fibers or laments forming the filter plug is stabilized by a plurality of points of adhesion between the individual bers as described above.

A method of producing such points of adhesion is` based on the fact that crossing synthetic fibers adhere to one another if the point of crossing is sufficiently compressed.

YIf a fiat loose ber web formed of such synthetic fibers or filaments is produced in which the fibers or filaments lie in any direction, a large number of crossing points be- .tween individual fibers corresponding Vto the very large Y treated is too rigid and strong for the purpose of manufacturing lter plugs.r A gradual consolidation of the ber web is quite sufiicient; the latter being compressed not across its entire fiat Width but only along a suitable fiat embossing design.

The embossing design may be produced, by way of example, by means of fiat dies having a ribbed pressing surface or again by means of rotating rollers having a corresponding design formed of projecting edges on the roller surface. The last-named case is represented, by Way of example, in the device according to FIG. 4, all less essential details being omitted. The ber web formed of the synthetic or regenerated cellulosic fibers'such as viscose fibers is processed in the known manner by the mechanism 21. By Way of example, the mechanism 21 Y; may be designed as a card or a converter of usual design,

the great advantage over cellulose acetate bers that they i are not foreign but akin to the human organs. Any fiber particles which, during use, pass into the respiratory organs and, in particular, into the lung in the form of dust which can never be entirely elimina-ted, soon lose their dangerous splinter structure by swelling on the moist mucous membranes, their edges and points will become rounded, they become supple and are then similarly harmless as natural ber lengths. When swelled, the hydrophile synthetic fibers have very little iioating power, which facilitates their natural removal from the respiratory organs. The term synthetic bers as used throughout the specification and claims is meant to encompass also regenerated cellulose fibers.

The hydrophilic and swelling synthetic bers or laments described and those of similar behaviour, however, could not vreadily be processed into filter plugs. Their high swelling capacity-indispensable for the increase of their absorptive power and for hygienic reasons-causes the individual fibers to be come soft, tacky and supple When such filter plugs are used, while the bundled fibers klose their shape and strength, which all results in a highly undesirable increase of the resistance to pulling. This it being of advantage for certain applications to employ relatively short-stapled material. lThe mechanism 21 applies a loose and thin ber web 22 to the endless belt 23 which travels in the direction indicated by the arrow. This belt 23 passes around the roller 24 which serves Ias a counter-roller for an embossing roller 25. The surface of the embossing roller 25 is provided with a design of projecting irregularities, e.g. intersecting oblique ribs -as indicated in FIG. 4. The roller 25 forces the ber web k22 passing beneath it against the supporting belt 23 and the counter-roller 24 so that the embossing ribs on the circumference of the embossing roller 25 produce a corresponding embossed design visible on therrconsoldated and self-supporting ber web 26 which emerges from the n roller 25. n

If desired, the embossing roller 25V can be heated in addition, e.g. by means of lan electric heating element 27 which is supplied with heating current via the slip-rings 28 and the lines 29. Such heating of the embossing roller-25 is particularly indicated when thermoplastic synthetic bers are employed. Y

The self-supporting ber web 26 is taken up after leaving the embossing roller 25 and formed into a rollV 30 Vby means of known take-up devices.

FIGS. 5 to 9 show `a number of embossing designs suited to gradual consolidation of the ber web. Although the self-supporting ber web produced is still very loose and can be of practically any desired thinness, the surface of therweb facing the embossing roller clearly shows the pressed design. This design can consist of lozenge-type intersecting lines running obliquely to the webs direction of travel as shown in FIG. 5, or of lines parallel with or normal to the longitudinal axis of the said web as shown in FIG. 6. An Vembossing design without intersecting lines z is shown in FIG. 7 and other line designs `are represented in FIGS. 8 and 9. Essentially, any embossing design can be employed which ensures that a sufficient number of points of crossing of individual bers or laments disposed in random directions will be pressed together. A design comprising only embossed points is less suitable unless the ber web is extremely dense.

It is also possible to add to the ber web 22 formed of the described hydrophilic and swelling synthetic bers a certain quantity of other fibers of both natural and synthetic origin. If natural bers such as cellulose fibers, cotton bers and the like are added, the consolidation described can also be obtained by creating a network of points of adhesion by means of embossing a design, experience showing that a natural fiber and a synthetic or regenerated cellulosic fiber such as a viscose ber will adhere to one another at a point of crossing after embossing. Instead of natural bers, the ber web formed of hydrophilic and swelling synthetic or regenerated fibers may, by way of example, be given an addition of a certain quantity of synthetic fibers having a lesser swelling capacity, or of cellulose acetate fibers, which may be Aadvantageous if the absorptive action of the'hydrophilic -synthetic fibers is too powerful; in this case, too, consolidation may be obtained by embossing a design. The fiber web consisting of hydrophilic and non-hydrophilic synthetic bers may be advantageous also inasmuch as the non-swelling synthetic fibers retain their stiffness also when the lter plug is used and thus operate as a supporting framework for the softened hydrophilic synthetic fibers.

Mention should finally be made of the fact that several fiber webs consisting at least partly of hydrophilic synthetic bers can be superposed to produce an endless filter rope. Such individual ber webs can `also be attached to one another as the two filter webs 33, 34 of FIG. 10 which have individually been provided with a design of points of adhesion, and which are'interconnected by a plurality of embossing grooves oriented in the longitudinaldirection of the webs according to a predetermined embossing design. Naturally, more than two ber webs can be, interconnected in this manner, as the three such webs according to FIG. 11.

An embodiment of the second unitof the mechanism for the manufacture of a filter rope suitable for processing into filter plugs is shown in FIGS. 12a and 12b. A conveyor device comprising the two rollers 4i) and 41 and the conveyor band 42 is supplied with two lter webs 43 and 44 already consolidated, which are delivered by delivery rolls 4S and 46 respectively. The preceding consolidation of these loose and very thin filter webs in a first mechanism such as the one according to FIG. 4

enables such webs to be wound up and off at least once. The two superposed filter webs 43 and 44 are here supplied, by the conveyor unit, to a pair of rollers 47 and 4S which are, by way of example, equipped with'a large number of meshing annular ribs 49 and 50 respectively of which the annular ribs 49 of the top roller 47 are shown in FIG. 12b. The lter web 51 emerging from between the rollers 47 and 48 passes into a gathering device 52 of known design and is there gathered into a filter rope 5S transversely to its direction of travel, the said lter rope having a circular or oval cross-section as desired.

The engaging annular ribs 49 and 50 of the two rollers 47 and 4S can be designed so that the faces of the ribs force the lter web passed beneath them against the sole surfaces of the corresponding groove in the counter-roller or that the lter web is compressed between the opposing flanks of the individual ribs of the two rollers. In the one case, a filter web having a wavy cross-section as shown diagrammatically in FIG. 13a will be produced, which is provided with consolidated areas at the highest and lowest points, which are substantially parallel with the axis of the filter web. In the second case, a wavy filter web is again obtained of which the cross-section substantially corresponds to that shown diagrammatically in FIG. 13b, in which the lateral fianks 56 of the waves are provided with consolidated areas 55 which again extend substantially parallel with the lter web axis. It is obvious that the meshing annular ribs may be replaced by other suitable surface irregularities projecting from the surface of the rollers 47 and 48, provided that care is taken for the filter web passing between them to obtain a longitudinal structure of consolidated areas. These consolidated areas need not be continuous in the longitudinal direction, but may be discontinuous. The wave-like structure of the lter web substantially resembling that shown in FIGS. 13a, 13b produced by rolling with engaging annular grooves has proved particularly advantageous because ber material so deformed can subsequently readily be transformed into a circular filter rope 53 by the gathering device, and because this filter rope possesses, after being processed into filter plugs, particularly favourable properties. In particular, the consolidated longitudinal areas extending along the lter plug result in a further improvement of the mechanical properties of the lter plug during use, and their action complements that of the framework of points of adhesion.

If desired, a ber web 51 may also be produced which is not wavy but possesses a cross-section substantially similar to that shown diagrammatically in FIG. 13C, i.e. which is approximately fiat while still being provided with consolidated areas 55 extending in the longitudinal direction of the web.

In the diagrammatic views according to FIGS. 13a to 13C, the consolidated areas formed by compressing the fiber material are designated at 55, while the unprocessed ber material between the said areas is designated at 56. Attention is called to the fact that the second part of the mechanism according to FIGS. 12a, 12b constitutes only an embodiment. It is also possible to provide, instead of the two delivery rollers 45 and 46, a single such roller and to supply only one filter web to the conveyor unit. Conversely, more than two such filter webs may be superposed. If desired, the strength of the filter webs can be influenced by more than one such pair of rollers and various types of longitudinal structures be created in the filter web. Furthermore, the rollers provided to influence the filter webs may also be heated similarly to the roller 2S in the mechanism according to FIG. 4.

The present method enables a web of thin and loose 4fibers in which the individual fibers o r ber tufts are not interconnected to be transformed'into a self-supporting ber web of the nature of aparticularly light fabric similar to a muslin bandage used for medical purposes. Instead of weaving the individual fibers, which is not possible with conventional means at the disposal of textile processes owing to the very thin fibers, the present method provides a pressing process. Accordingly, if the embossed design is selected properly, the product may be described as constituting a pressed fabric. The novelty of the lter plugs according to this invention thus resides in the fact that when opened-prior or subsequent to use-it can be spreadL to form a fabric-type ber 'web which constitutes the said pressed fabric. This constitutes a characteristic difference when compared with the known filter plugs also consisting of fibers or a fiber bundle.

I claim:

1. A filter lplug for cigarettes and the like, consisting essentially of superposed layers of comparatively loose fibrous material arranged so that abutting faces of said superposed layers extend in axial direction of said filter plug, each of said layers of fibrous material comprising haphazardly arranged bers, which are adapted lto absorb moisture under simultaneous swelling and which are also adapted to 'be mechanically deformed by compression of selected portions of the layer and thereby adhere and be joined together `due to such mechanical deformation 7 so that the compressed portions of said layer composed of said mechanically deformed liber por-tions have greater mechanical strength and lesser capability of absorbing moisture and of Iswelling than uncompressed portions of Isaid layer, each of said fibrous layers including a plurality -of `said compressed portions composed of mechanically deformed and thereby joined fiber portions extending throughout the thickness of the respective layer, thereby forming reinforcing structures which will be substantially unaffected by moisture passing through said filter plug during use of the same.

2. A filter plug for cigarettes and the like, consisting essentially of a vspirally wound layer of comparatively loose fibrous material arranged so that abutting face portions of said spirally wound layer extend in axial direction of said filter plug, said layer of fibrous material comprising haphazardly arranged fibers which Iare adapted to absorb moisture under simutlaneous swelling and which are also adapted to be mechanically deformed by compression of selected portions -of the layer and thereby adhere and be joined together due to such mechanical deformation so that the compressed portions of said layer composed of said mechanically deformed fiber portions have greater mechanical strength and lesser capabil-i-ty of absorbing moisture and of swelling than uncompressed portions of said layer, each of `said fibrous layers including a plurality of said compressed portions composed of mechanically deformed and thereby joined fiber portions extending throughout the thickness of said layerthereby forming reinforcing structures which will be substantially unaffected by moisture passing through said filter plug 4during use of the same.

3. A filter plug for cigarettes and the like, consisting essentially of superposed layers of comparatively loose fibrous material arranged so that abutting faces of said superposed layers extend in axial direction of said filter plug, each of said layers of fibrous material comprising haphazardly arranged viscose fibers which are adapted to absorb moisture under simultaneous swelling -and which are also 'adapted to be mechanically deformed by compression of selected portions of the layer and thereby adhere and be joined together due to such mechanical deformation so that the compressed portions of said layer composed of said mechanically deformed fiber portions have greater mechanical strength and lesser capability of absorbing moisture and of swelling than uncompressed portions of said layer, each of said fibrous layers including a plurality of said compressed portions composed of mechanically deformed and thereby joined fiber portions extending throughout the thickness of the respective layer, lthereby forming reinforcing structures which will be substantially unaffected by moisture passing through `said filter plug during use of the same.

4. A filter plug for cigarettes -aud the like, consisting essentially of a gathered flexible web of comparatively loose fibrous material forming a plurality of folds with abutting faces of adjacent folds engaging each other and extending in axial direction of said filter plug, said web of fibrous material comprising haphazardly arranged fibers which are adapted to absorb moisture under simultaneous swelling and which are also adapted to be mechanically deformed by compression of selected portions of the Yweb and thereby adhere and be joined together `due to such mechanical deformation so that the compressed portions of said web composed of s-aid mechanically deformed fiber portions have greater mechanical strength and lesser capability of absorbing moisture and of swelling than uncompressed portions of said web, said fibrous web including a plurality of said compressed portions composed of mechanically deformed and thereby joined fiber 'porti-ons, extending through the thickness of said web thereby yforming reinforcing structures which will be substantially unaffected by moisture passing through said filter plug during use of the same.

I 5. A fil-ter plug according to claim 1, wherein said haphazardly arranged fibers consist at least partly of synthetic fibers and filaments the cross sections of which are adapted to increase at least by 100% on swelling.

6. A filter plug according to claim 1 vwherein said Y haphazardly arranged fibers vcomprise hydrophilic synthetic fibers capable of absorbing at their surfaces liquid components of tobacco smoke.

7. A filter plug according to claim 1 wherein said i haphazardly arranged fibers comprise synthetic fibers with a moisture absorption of at least 10% in an atmosphere of relative humidity. y 8. A rl'ilter plug according to claim l wherein said haphazardly arranged fibers comprise synthetic fibers with a moisture absorption of at least 25% in an atmosphere -of relative humidity. w Y y 9. A filter plug according to claim l wherein said haphazardly arranged fibers comprise cellulose and viscose fibers.V Y Y Y Y n l0. A flterrplug laccording toclaim9 wherein said haphazardly arranged fibers include between 5 and 50% by weight of viscose fibers. Z A v Y 4 A Y l1. A filter plug according to claim 1 wherein said haphazardly arranged fibersconsist essentially of cellulose fibers and thermoplastic synthetic fibers`v g p k g 12. A filter plug accordingto claim` I wherein said haphazardly arranged fibers consist essentially of cellulose fibers and hydrophilic acetate fibers.

References Cited in the file of this patent UNITED STATES PATENTS 850,151 Goldman Apr. 16, 1907 1,409,206 Van Nostrand Mar. 14, 1922 2,085,293 Butiington June 29, 1937 2,228,383 Berl Jan. 14, `1941 2,464,301 Francis Mar. 15, 1949 2,592,470 Ryberg Apr. s, 1952 2,705,686 Ness et al. Apr. 5, 1955 2,705,692 Petterson Apr. 5, 1955 2,707,960 Janecke May 10, 1955 2,737,997 Himmelheber et al Mar. 13, 1956 2,763,267 Mller Sept. 18, 1956' 2,801,638 Schur et al. Aug. 6, 1957 2,881,769 Touey Apr. 14, 1959 2,891,279 Neumann lune 23, 1959 2,904,050 Kiefer et al Sept. 15, 1959 

1. A FILTER PLUG FOR CIGARETTES AND THE LIKE, CONSISTING ESSENTIALLY OF SUPERPOSED LAYERS OF COMPARATIVELY LOOSE FIBROUS MATERIAL ARRANGED SO THAT ABUTTING FACES OF SAID SUPERPOSED LAYERS EXTEND IN AXIAL DIRECTION OF SAID FILTER PLUG, EACH OF SAID LAYERS OF FIBROUS MATERIAL COMPRISING HAPHAZARDLY ARRANGED FIBERS, WHICH ARE ADAPTED TO ABSORB MOISTURE UNDER SIMULTANEOUS SWELLING AND WHICH ARE ALSO ADAPTED TO BE MECHANICALLY DEFORMED BY COMPRESSION OF SELECTED PORTIONS OF THE LAYER AND THEREBY ADHERE AND BE JOINED TOGETHER DUE TO SUCH MECHANICAL DEFORMATION SO THAT THE COMPRESSED PORTIONS OF SAID LAYER COMPOSED OF SAID MECHANICALLY DEFORMED FIBER PORTIONS HAVE GREATER MECHANICAL STRENGTH AND LESSER CAPABILITY OF ABSORBING MOISTURE AND OF SWELLING THAN UNCOMPRESSED PORTIONS OF SAID LAYER, EACH OF SAID FIBROUS LAYERS INCLUDING A PLURALITY OF SAID COMPRESSED PORTIONS COMPOSED OF MECHANICALLY DEFORMED AND THEREBY JOINED FIBER PORTIONS EXTENDING THROUGHOUT THE THICKNESS OF THE RESPECTIVE LAYER, THEREBY FORMING REINFORCING STRUCTURES WHICH WILL BE SUBSTANTIALLY UNAFFECTED BY MOISTURE PASSING THROUGH SAID FILTER PLUG DURING USE OF THE SAME. 